Simultaneous voice and modem data transmitted over the same communications link between two sites has been accomplished in several ways. The most common communications link used between two sites is the telephone line. The most common data handling equipment to communicate over a communications link is the computer modem which modulates digital data onto a carrier for transmission in the voice band of the telephone line. A wide variety of modulation standards have been promulgated by such international groups as the CCITT for communication in the voice band. The data bandwidth for such modulation standards is typically fixed and the throughput rate of data is also assumed to be fixed.
In some modulations standards, there are provisions for changing the modulation data rate based on the quality of the communications link. For example, in a noisy telephone line, a 9600 baud modulation rate may have such a high bit error rate that the modulation must be changed to a 2400 baud connection. This is done in a handshake communication protocol between the two sites when the communications link simply cannot support the higher rate.
There is a need in the art, however, for an efficient and cost effective way of maximizing bandwidth over the communications link between two sites to enable the simultaneous transmission of voice and data. There is a need, therefore, to negotiate the data bandwidth between the sites, negotiate the compression rate for the voice compression algorithms used to compress the voice and there is a need to allocate and reallocate the ratio of compress voice to digital data transmitted over the communications link.